From 35C3 Wiki


A GSM/UMTS network is provided at the 35C3 and operated by Osmocom during the conference.

You can use the GSM/UMTS network to place calls or send SMSs for free on the GSM/UMTS network as well as to the on-site DECT, ISDN, POTS and VoIP networks of the POC. To use the network you require a congress SIM card.

UMTS for internet or data traffic is experimental/unstable.

To operate the GSM/UMTS network the free software implementation osmocom is used. If you want to know more about it, talk to the GSM team located at CCH 0, near the POC. Also, if you don't have see the GSM/UMTS signal at your place, please let us know so we can improve the coverage.


The network is the opportunity to test on a large scale the Osmocom stack and improve it. Accordingly some aspects might not yet be stable.

What works:

  • you can buy a SIM card at the POC and Späti for 3 Euros
  • register your extension using your GSM token
  • the GSM and UMTS network are running
  • phones can register to the GSM/UMTS network
  • send SMSs between phones
  • voice calls (over GSM/UMTS, to/from DECT/SIP)

What does not yet work:

  • very old GSM-only phones (e.g. candybar form-factor) can only send SMSs, but can't make voice calls (they don't support the codec also used by UMTS phones)
  • internet over UMTS is very unstable
  • GPRS (internet over GSM) is disabled

SIM card, registration

To be able to use the GSM network, you require a SIM Card dedicated for this network. It is required to encrypt the traffic over the air:

  1. Use a SIM card from past CCC events, or acquire a new one at the POC or Späti.
  2. Register/log-in on GURU3.
  3. Register a new extension with phone type "GSM handset".
  4. Dial the GSM token shown by click on the key next to your extension. This step completes the registration process and pairs your device/SIM with the event's GSM network. If you ever feel like switching devices or SIM cards, then just redial this number on your new device.

note: the SIM card also works without using the token, but only within the GSM network.

Mobile data over UMTS

To use data over UMTS you need to set up an APN.

Under Android go to Settings -> Wireless & Networks -> More -> Cellular networks -> Access Point Names. You only need to set the APN to "internet" and the APN protocol to IPv4.


The UMTS network operates on Band V (850 MHz). Most feature phones and some smartphones do not support this band. You can check on phone databases such as PhoneArena or phonedb.

UMTS is enabled by default. Dial *#300# to disable it.

NOTE: the status is not synchronized with GURU3. dial *#102# to know your current state.

Additional information

  • To get your extension, dial *#100#.
  • To get your IMSI, dial *#101#.
  • To know in which network you are (GSM or UMTS), dial *#102#.
  • You can be called from the outside. For more information and outside phone number visit the Linux-Call-Router project.
  • You can re-use the GSM token you got when creating an extension with any SIM for this network.
  • The MCC (Mobile Country Code) is 262 (Germany), the MNC (Mobile Network Code) is 42.
  • Our network use the following bands:
    • GSM (1800 MHz / DCS)
    • UMTS (850 MHz / band V)

Related Projects

Archived page - Impressum/Datenschutz